Although, as well known to those skilled in the art, there is a diverse set of chemical formulations that can be used to prevent or suppress the formation of a foam (an anti-foam composition) and/or to eliminate or reduce a volume of foam after foam formation (a defoamer composition), in practice, the terms are used somewhat interchangeably. This may be due, in part, to the fact that most foam treating formulations exhibit some degree of both anti-foam and defoaming properties. For the purpose of this disclosure, therefore, the term foam control composition will be used to encompass those compositions and formulations that exhibit anti-foam and/or defoaming activity. A general characteristic of most foam control compositions is the combination of surface activity and being highly insoluble in aqueous solutions. Many foam control compositions are formulated as an emulsion that, in combination with its surface-active nature results in rapid spreading onto any air-water interface that it encounters. Some defoamers include particles including, for example, hydrophobized silica particles or ethylene-bis-stearamide particles, that pierce the surfaces of foam bubbles and cause the smaller bubbles to coalesce or agglomerate as the defoamer spreads along the interface.
Although many earlier conventional foam control compositions utilized one or more oils as the main ingredient, there are increasing concerns about chlorinated organic products resulting from, for example, chlorine bleaching of the residual organic components during subsequent processing. This was of particular concern within the pulp and paper making industries and has led to increased use of reduced or low-oil compositions and/or oil-free compositions using, for example, silicone-based compositions that generate less cause for concern during downstream processing.
The persistence of foam in various industrial processes can cause process inefficiencies and, in some cases, degrade one or more properties of the final product. For example, when treating produced water from steam assisted gravity drainage systems, foam control compositions are often used to prevent or suppress foam formation in the evaporators being used to reclaim the produced water. Although silicone-based foam control compositions are generally effective in suppressing foam formation, silicone-based can tend to form films on heat transfer surfaces within the equipment. These films can, in turn, produce undesirable effects including, for example, impeding heat transfer into the process fluid and/or acting as a point of adhesion for other deposit forming substances.
As the name implies, oil-based foam control compositions utilize an oil carrier including, for example, one or more oils selected from a group including mineral oils, vegetable oils, white oils and/or any other oil that is generally insoluble in the foaming medium. Oil-based foam control compositions may also incorporate one or more waxes and/or particulates, for example, hydrophobic silica, in order to improve the performance. Waxes typically used in such applications include, for example, ethylene bis stearamide (EBS), paraffinic waxes, ester waxes and fatty alcohol waxes. These oil-based foam control compositions may also include one or more surfactants in order to improve emulsification and spreading within the foaming medium.
Water-based foam control compositions include different types of oils, often white oils or vegetable oils and waxes, often one or more long chain fatty alcohols, fatty acid soaps or esters, dispersed in a water base.
As the name implies, silicone-based foam control compositions utilize one or more a silicone compounds as the active component. These might be delivered as an oil or a water-based emulsion. The silicone compound frequently consists of hydrophobic silica particles dispersed in a silicone oil. A range of emulsifiers can be utilized to improve the ability of the silicone compound(s) to spread easily and quickly throughout the foaming medium. The silicone-based foam control compositions may also contain silicone glycols and other modified silicone fluids. Silicone based foam control compositions may also be utilized for suppressing foams in non-aqueous foaming systems experienced in certain industries including, for example, the production of crude oil and associated oil refining operations. For very challenging applications, fluorosilicones may provide improved performance.
EO/PO based foam control compositions contain polyethylene glycol and polypropylene glycol copolymers and are typically delivered as oils, aqueous solutions, or water-based emulsions. EO/PO copolymers normally have good dispersing properties and may be preferred in those applications in which surface deposit problems are an issue. Additional background information on the history, formulation and use of foam control compositions may be found in editor Garret, P. R.'s Defoaming: Theory and Industrial Applications (1992), Surfactant Science Series 45 CRC Press ISBN 0-8247-8770-6, the entire contents of which are incorporated herein by reference.